employment contracts

I am in the process of reviewing a draft employment contract for a small retail soft furnishings business where the following condition has been set:

Non Competition,
During the term of the employees employment and for a period of 1 year after the end of that term.
A,the employee will not,absent the prior written consent of the employer,which will be withheld only for the purpose of protecting the employers business interest.
B,be directly or indirectly involved with a business that is in direct competition with the particular business line of the employer and that is within east and west sussex miles.

My questions:
A,Can an employer put a ban on an employee from working in their chosen profession over such a large area bearing in mind this is a one shop retailer?.
B,If an employee decides to open their own business in their chosen profession what is the recommended business area that should be observed?
C,How leagally binding could this be?

Hope you can assist.
Kind regards
Steve